The present invention relates to a stopping mechanism for the weft thread insertion device of a weaving loom. More particularly, the invention relates to a brake for the insertion device and a detector for determining the position of the insertion device in the stopping mechanism.
Stopping mechanisms of this kind are used especially in looms operating with gripper shuttles. These looms include a large number of gripper shuttles in continuous circulation which must come to a standstill in approximately the same position. Since the various gripper shuttles have certain individual differences, the braking device requires constant readjustment while the loom is in operation. Readjustment is achieved by reference to the position of the gripper shuttles in the stopping mechanism as determined by the detector.
Various catching mechanisms for use in gripper shuttle looms are known in the prior art. For example, U.S. Pat. No. 3,124,166 to Pfarrwaller discloses a shuttle receiving mechanism for a gripper shuttle loom including a brake for stopping the shuttles at a predetermined location within the shuttle receiving mechanism. The catching mechanism includes a pair of "feelers" provided along the shuttle path indicating the stopping position of the shuttle. A first feeler is positioned at a portion of the shuttle path which defines the minimum length of the shuttle path and a second feeler is positioned at another portion of the shuttle path which corresponds to the maximum length of the shuttle path. Thus, the gripper shuttles ideally stop at a position between the first feeler and the second feeler. If the shuttle does not stop in the desired location, the brake is adjusted until the shuttle stops between the first feeler and the second feeler. A similar catching device for a gripper shuttle loom is disclosed in U.S. Pat. No. 4,192,354 to Pfarrwaller.
Other prior art detector devices for gripper shuttle loom catching mechanisms operate on the principle of magnetic induction and in most cases use several sensors for each stopping mechanism. Apart from the fact that as the demand for accuracy in determining the position increases the number of sensors and hence the expense of the system increases, these detector devices also entail certain restrictions in construction since the detectors must be arranged near or possibly inside the braking device, thus causing space problems and preventing optimum layout of the braking device. Another disadvantage of these known detectors arises from the fact that new designs of gripper shuttles contain an ever increasing proportion of plastic materials and a reduced amount of steel so that inductive sensors suitable for detecting the shuttles are increasingly bulky and thus considerably aggravate problems associated with space limitations.
The present invention provides a gripper shuttle loom stopping mechanism in which the detector device determines the position of the gripper shuttle with a high degree of resolution and can be installed at a considerable distance from the brake. Additionally, the detector device of the present invention requires no mechanical objects to be positioned within the path of the gripper shuttle.